Light-curing technology: past, present, and future.

The availability of light-curable resin systems has led to the development of a variety of technologies for producing the light necessary to cure them. Light, being electromagnetic radiation, is comprised of a wide spectrum of energies including ultraviolet, visible, and infrared. Each wavelength region of light has different characteristics in terms of chemical reactions, most notably polymerization of dental materials. Quartz tungsten halogen, plasma arc curing, laser, and, recently, light-emitting diode have all been important technologies used to produce light through dental curing units. Each technology has unique advantages and disadvantages. Thus, it is important for dental professionals to understand the polymerization processes and the ways in which these processes are affected by light energy.